Estimating the propagation characteristics of large‐scale traveling ionospheric disturbances using ground‐based and satellite data

Abstract

In this article, the propagation characteristics of large‐scale traveling ionospheric disturbances (LS TIDs) are estimated during the geomagnetic storm periods of 14–16 May 2005 and 25–27 September 2011 over South Africa. One and two GPS arrays have been independently considered for the storms of 15 May 2005 and 26 September 2011, respectively. The average periods of dominant modes (≈ 2.5–3.5h) in the time series data were determined by applying wavelet analysis on both ionosonde and GPS data. The consideration of diurnal GPS total electron content (TEC) variability from receivers along three different longitude sectors showed a time shift in TEC enhancement with increasing latitude, the first indication of equatorward motion of the traveling ionospheric disturbances (TIDs). The statistical method (based on GPS radio interferometry) employed shows that these TIDs were mostly propagating nearly equatorward (for both storm periods), which is consistent with the existing literature about storm‐induced TIDs. On storm days, TID horizontal velocities have been determined in the range of ≈200–500m/s. The analysis of diurnal TEC response from different stations confirmed that the positive storm effect observed on 15 May 2005 was a result of the large‐scale TIDs of wavelength ≈4000 km. On the other hand, the estimated wavelengths of LS TIDs on 26 September 2011 were ≈2400–3400km between 10 and 17 UT. A time lag is observed between the times at which enhancements in TEC, ionosonde foF2, and hmF2 data are revealed, and this has been attributed to the passage of the TID.

Statistical analysis of TEC perturbations over a low latitude region during 2009–2013 ascending solar activity phase

“…Different methods have been used to detrend TEC to identify TID in TEC perturbations. For example polynomial fitting (Katamzi et al, 2012;Habarulema et al, 2013a) and moving average (Hernández-Pajares et al, 2006) have all performed quite well. Without introducing artificial periodicities in the TEC data, we applied a least square polynomial fit of degree 6 to the vTEC.…”

GPS observation of continent‐size traveling TEC pulsations at the start of geomagnetic storms

“…Analyses of these two storm events by other investigators also indicated very similar pattern at various locations around the globe. Ionosonde observations in the South African sector [ Habarulema et al , ] on 26 September 2011 show that TID signatures only started to appear at ∼18:00 UT, and no sign of significant oscillations in the ionosphere had been observed since the SSC (∼12:30 UT) until ∼18:00 UT. For the 24/25 October 2011 storm, ionosonde data from S.J.…”

“…Likewise, the calculated scale size of the observed SS-TECP appears to be significantly larger than the typical wavelength of most ionospheric disturbances. The propagation speed and wavelength of LSTIDs are generally found in the range of 100-1000 m/s and 600-3000 km [see, e.g., Nicolls et al, 2004;Lee et al, 2008;Ding et al, 2008;Habarulema et al, 2013]. There are a few types of disturbances in high-latitude ionosphere (mainly from all-sky airglow measurements) that do propagate at a speed of several km/s, such as the westward traveling surge [Akasofu, 1964;Kan et al, 1984] or the longitudinally propagating arc waves reported by Uritsky et al [2009].…”

Study of ionospheric disturbances over the China mid- and low-latitude region with GPS observations

“…Hernández-Pajares et al (2011) provided ionospheric monitoring based on GNSS measurements and assessed TIDs, solar flares, ionospheric storms and scintillation. Habarulema et al (2013) estimated the propagation characteristics of large-scale TIDs (LSTIDs) during geomagnetic storm, and showed that disturbances were mostly propagating nearly equatorward. Ding et al (2014) comparatively investigated ionospheric disturbances over North America and China based on GPS dense regional observations.…”